1. Field of the Invention
The present invention generally relates to a balanced transmission cable connector, and particularly relates to a balanced transmission cable connector having a contact assembly attached to an end of the cable through a relay board, a group of plural input contacts to input a signal and a group of plural output contacts to output a signal so as to reduce crosstalk between the input signal and the output signal.
2. Description of the Related Art
Data transmission is accomplished by two major methods. One is an imbalanced transmission method in which a single wire is used for every data element. The other one is a balanced transmission method in which two wires in pairs are used for every data element to simultaneously transmit a positive signal and a negative signal. The magnitudes of the positive signal and the negative signal are equal, and the transmission directions are opposite. The balanced transmission method has an advantage of being less affected by noise than the imbalanced transmission method, and therefore the balanced transmission is now increasingly used in high-speed signal transmission.
FIG. 1 is an illustration showing a balanced transmission cable connector 10 connecting a computer 1 and a server 2. The cable connector 10 includes a cable 11 having connector sections 12 and 20 one on each end thereof. The connector section 12 includes signal output contact pairs (1) through (4) and signal input contact pairs (5) through (8). Likewise, the connector section 20 includes signal output contact pairs (1) through (4) and signal input contact pairs (5) through (8).
A signal from the computer 1 is transmitted to the sever 2 via the signal output contact pairs (1) through (4) of the connector section 12, the cable 11, and the signal input contact pairs (5) through (8) of the connector section 20 with the balanced transmission method. A signal from the server 2 is transmitted to the computer 1 via the signal output contact pairs (1) thorough (4) of the connector section 20, the cable 11, and the signal input contact pairs (5) through (8) of the connector section 12 with the balanced transmission method.
Crosstalk is likely to occur between an input signal transmission line and an output signal transmission line adjacent thereto.
FIGS. 2A through 4 are illustrations each showing a part of a related-art balanced transmission cable connector 30 of a type disclosed, for example, in Japanese Patent Laid-Open Publication No. 2003-059593. Lines X1–X2, Y1–Y2 and Z1–Z2 respectively indicate the width direction of the cable connector 30, the longitudinal direction thereof and the height direction thereof. Y1 and Y2 respectively indicate the rear side and the front side. When referring to arrangement of contacts, the lines Z1–Z2 and X1–X2 respectively indicate the column direction and the row direction. FIG. 2A is a top perspective view of the cable connector 30, and FIG. 2B is a bottom perspective view of the cable connector 30. FIG. 3 is a side elevational view showing the cable connector 30, and FIG. 4 is an illustration showing a cable connected to an end of a relay board 40.
The cable connector 30 has a contact assembly 31, the relay board 40, a balanced transmission cable 130, and a shield cover 150.
FIG. 5 is a partly exploded perspective view showing the contact assembly 31. In FIG. 5, the contact assembly 31 has an electrical insulating block body 32. The block body 32 includes plural first and second signal contacts 33 and 34 and plural plate ground contacts 35 therein. The first signal contacts 33 are respectively paired with the second signal contacts 34 in the column direction (Z1-Z2 direction). The plural pairs of first and second signal contacts 33 and 34 and the plural ground contacts 35 are alternately arranged at regular intervals P in the row direction (X1-X2). The block body 32 has a plug body section 32a projecting toward the Y2 side. The plug body section 32a has an array of grooves. The first and second signal contacts 33 and 34 respectively have first and second signal contact sections 33a and 34a and first and second finger sections 33b and 34b. The ground contact 35 has a ground contact section 35a and a fork section 35b. The first and second signal contacts 33 and 34 and the ground contacts 35 are incorporated in the block body 32, just like being inserted from the Y1 side toward the Y2 direction. The first signal contact sections 33a are disposed on the upper face of the plug body section 32a and the second signal contact sections 34a are disposed on the lower face of the plug body section 32a. Upper and lower edges of each ground contact section 35a are respectively exposed on the upper and lower faces of the plug body section 32a. The first and second finger sections 33b and 34b and the fork sections 35b are so disposed to project to the Y1 side of the block body 32.
Two signal contacts form a contact pair. The contact assembly 31 has eight contact pairs (1) through (8) arranged in order. The contact pairs (1) through (8) are a group of signal output contact pairs (1) through (4) and a group of signal input contact pairs (5) to (8).
FIGS. 6A and 6B are illustrations of the relay board 40. As shown in FIGS. 6A and 6B, the relay board 40 is a generally square-shaped multilayer board having a ground layer (not shown) inside. The relay board 40 has, on an upper face 41 at the Z1 side, contact connection pads 51 through 58 arranged along the edge at the Y2 side, wire connection pads 61 through 68 arranged along the edge at the Y1 side, parallelly-arranged wiring patterns 71 through 78 respectively extending in the Y1-Y2 direction for connecting the contact connection pads 51 through 58 and the wire connection pads 61 through 68, and a ground pattern 80 covering the rest of the surface of the upper face 41. The ground pattern 80 shields between adjacent contact connection pads, between adjacent wiring patterns and between adjacent wire connection pads. The relay board 40 also has, on a lower face 42 at the Z2 side, contact connection pads 91 through 98 arranged along the edge of the Y2 side, wire connection pads 101 through 108 arranged along the edge of the Y1 side, parallelly-arranged wiring patterns 1111 through 118 extending in the Y1-Y2 direction for connecting the contact connection pads 91 through 98 and the wire connection pads 101 through 108, and a ground pattern 120 covering the rest of the surface of the lower face 42. The ground pattern 120 shields between adjacent contact connection pads, between adjacent wiring patterns and between adjacent wire connection pads.
FIGS. 7A and 7B are illustrations each showing the balanced transmission cable 130. As shown in FIG. 7A, the cable 130 has a double-shielded structure, having an outer shield 137, a shield wire mesh 138, and eight pair wires 141 through 148 arranged therein. Referring to FIG. 7B, each of the pair wires 141 through 148 comprises a pair of first and second shielded signal wires 132-1 and 132-2 and a drain wire 136 bundled and shielded by a metal tape 135 spirally wound thereon. The first and second shielded signal wires 132-1 and 132-2 and the drain wire 136 are outwardly extending from the end of each of the pair wires 141 through 148. The ends of the first and second shielded signal wires 132-1 and 132-2 are processed so as to expose bare first and second signal wires 133-1 and 133-2 by removing electrical insulating shields 134-1 and 134-2, respectively. The first and second signal wires 133-1 and 133-2 form a pair line. The end of the cable 130 is caulked by a clam member (not shown).
Referring back to FIGS. 2A through 3, the Y2 side end of the relay board 40 is fitted in the Y1 side of the contact assembly 31. The contact connection pads 51 through 58 are soldered to the first finger sections 33b of the first signal contacts 33, and the contact connection pads 91 through 98 are soldered to the second finger sections 34b of the second signal contacts 34. A part of each of the ground patterns 80 and 120 is soldered to the fork sections 35b of the ground contacts 35. In this way, the wire connection pads 61 and 101 are connected to the signal output contact pair (1); the wire connection pads 62 and 102 are connected to the signal output contact pair (2); the wire connection pads 63 and 103 are connected to the signal output contact pair (3); the wire connection pads 64 and 104 are connected to the signal output contact pair (4); the wire connection pads 65 and 105 are connected to the signal input contact pair (5); the wire connection pads 66 and 106 are connected to the signal input contact pair (6); the wire connection pads 67 and 107 are connected to the signal input contact pair (7); and the wire connection pads 68 and 108 are connected to the signal input contact pair (8).
The pair wires 141 through 148 at the end of the cable 130 are aligned in the X1-X2 direction. The first and second signal wires 133-1 and 113-2 extending out of an end of respective pair wires 141 through 148 are soldered to the Y1 side end of the relay board 40. The first and second signal wires 133-1 and 133-2 of the pair wires 141 through 148 are respectively arranged on the upper and lower sides of the end of the relay board 40. As shown in FIG. 4, the first signal wires 133-1 are soldered to the wire connection pads 61 through 68 with solders 160, and the second signal wires 133-2 are soldered to the wire connection pads 101 through 108 with solders 161. The drain wires 136 are soldered to the ground pattern 80 or 120. The ends of the pair wires 141 through 148 are arranged as shown in FIG. 4.
The contact pair (1) of the contact assembly 31 is electrically connected to the pair wire 141 through the contact connection pads 51 and 91, the wiring patterns 71 and 111, and the wire connection pads 61 and 101. The contact pair (2) of the contact assembly 31 is electrically connected to the pair wire 142 through the contact connection pads 52 and 92, the wiring patterns 72 and 112, and the wire connection pads 62 and 102. The contact pair (3) of the contact assembly 31 is electrically connected to the pair wire 143 through the contact connection pads 53 and 93, the wiring patterns 73 and 113, and the wire connection pads 63 and 103. The contact pair (4) of the contact assembly 31 is electrically connected to the pair wire 144 through the contact connection pads 54 and 94, the wiring patterns 74 and 114, and the wire connection pads 64 and 104. The contact pair (5) of the contact assembly 31 is electrically connected to the pair wire 145 through the contact connection pads 55 and 95, the wiring patterns 75 and 115, and the wire connection pads 65 and 105. The contact pair (6) of the contact assembly 31 is electrically connected to the pair wire 146 through the contact connection pads 56 and 96, the wiring patterns 76 and 116, and the wire connection pads 66 and 106. The contact pair (7) of the contact assembly 31 is electrically connected to the pair wire 147 through the contact connection pads 57 and 97, the wiring patterns 77 and 117, and the wire connection pads 67 and 107. The contact pair (8) of the contact assembly 31 is electrically connected to the pair wire 148 through the contact connection pads 58 and 98, the wiring patterns 78 and 118, and the wire connection pads 68 and 108. In short, the pair wires 141 through 144 are respectively connected to the signal output contact pairs (1) through (4), and the pair wires 145 through 148 are respectively connected to the signal input contact pairs (5) through (8).
In the cable connector 30, a signal transmission line of the signal output contact pair (4) is adjacent to a signal transmission line of the signal input contact pair (5). The signal transmission line of the signal output contact pair (4) and the signal transmission line of the signal input contact pair (5) are shielded by the ground contact 35 when in the contact assembly 31, and shielded by the ground patterns 80 and 120 when on the relay board 40. However, the first and second signal wires 133-1 and 133-2 at the end of the pair wire 144 soldered to the relay board 40 are not shielded from the first and second signal wires 133-1 and 133-2 at the end of the pair wire 145 soldered to the relay board 40. Therefore, crosstalk as shown with the arrows 170 and 171 possibly occurs at these non-shielded parts.